Sonoma Coast State Beach
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Sonoma Coast State Beach is a State of California property in Sonoma County consisting of public access use on lands adjoining the Pacific Ocean. This extent of beach runs from a coastal point about four miles north of Jenner and continues for approximately seventeen miles to the south to terminate at Bodega Head. The property lies along California State Route 1 and consists of a number of named beaches including Arched Rock Beach, Gleason Beach and Goat Rock Beach. The ecosystem consists of alternating sandy beaches and rocky shoreline, with a marine terrace extending above the entire extent with an upland California coastal prairie habitat.
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[edit] Geology
This strip of coastal property is subject to continuing marine erosion as well as windborne erosion, thus creating a situation where an average of one to three feet per year of land mass is lost. Obviously in years of heavy storms this value can be higher, whereas, in a less stormy year the land erosion can be lower. Over the last geologic epoch the land has been subject to uplift, a process which has created a marine terrace of the entire extent of the property. This marine terrace is elevated approximately 50 to 100 feet above mean sea level, which results in a steep bluff directly above the littoral zone.
Vertical rock formations are a geological hallmark of this site, and have weathered far less than the bulk of the soils. These features are known as sea stacks, and they appear standing out of the water or on the beach as though as sculptures placed decoratively along the shoreline. Occasionally these stacks appear as adornments on the marine terrace, indicating their ancient origin on the sea floor prior to uplift. These rock formations are composed of sandstone with layers of quartz.
The active San Andreas Fault runs roughly parallel and near to the coastline of Sonoma Coast State Beach. Soils within the site are classified as coastal beach sands (where rocky shoreline is not evident) and marine escarpment group soils on the marine terrace; typically soils above the marine terrace are in the Rohnerville loam group.[1] Most of the beach sands consist of a medium coarse brown to gray sandy materials, reflecting the high rate of erosion of escarpment soils into the ocean; however, there are patches of smooth pebble beach such as the approximately one hundred meter stretch lying immediately north of Goat Rock.
[edit] Ecology
The habitats include marine, littoral and coastal prairie. In the marine environment are found gray whales, harbor seals and California sea lions as well as a multitude of fish species and other marine organisms. There are also modest kelp beds and other marine vegetation. The littoral beach environment has fewer organisms than more southerly zones, because of the colder temperatures; however, there are tidepools which are abundant with marine flora and fauna.
The coastal prairie soils are moderately well drained and granular in nature with moderate soil permeability; these features lead to slight erosion potential and moderately high bio-productivity. Acidity of these loamy soils is medium to high, and thus some vegetative stunting and hospitality to rare plants is offered. The upland environment on the coastal prairie offers a variety of grasses and wildflowers including varieties of lupine, thistle and wild oats. The typical annual plant productivity is approximately 1500 kilograms per acre of air dried yield per annum in an abundant moisture year, and about half that amount in a very dry year. A variety of birds and mammals thrive on the coastal prairie including numerous California Mule Deer, Odocoileus hemionus californicus.
[edit] History
Some of the oldest natural history of this area related to mammals are a rock formation about one mile south of the Russian River. There is found a sea stack formation with prominent rubbing marks about two to four meters in elevation, a height too high to have been caused by modern bovids. Mammoths are believed to have roamed here as recently as 40,000 years ago, and they are thought to have created these severe rubbing marks[2]. Mammoth fossil remains have been found at Bodega Head at the south end of Sonoma Coast State Beach.
Earliest known human settlement of this site was by the Native American Coast Miwok and Pomo tribes. As early as 1849 archaeological finds were recorded on this property, and to date dozens of prehistorical kitchen middens and other types of tribal habitation finds have been made. The property is part of a Mexican land grant called Bodega Rancho. The Russians are thought to have begun logging the old-growth forests directly above the coastal prairie in the early 1800s.
The underwater delineation of the property is considered to extend to 1000 feet from the shoreline. While no shipwrecks have been discovered, the literature indicates that there are 17 vessels which may have been lost in these waters. There are remains of numerous historic barns and other agricultural buildings on the coastal prairie indicating 19th century settlement by Europeans; at Duncans Landing there are iron pins embedded in the sandstone bluffs as evidence of the active shipping industry here in the late 1800s and early 1900s.
[edit] References
- ^ Soil Survey, Sonoma County, California, U.S. Department of Agriculture, Soil Conservation Service, Government Printing Office, Washington DC, May 1972
- ^ E. Breck Parkman, Mammoth Rocks: Part 1, Where Pleistocene Giants got Good Rub, Center for the Study of the First Americans, Mammoths Series, Volume 18, Number 1, December 2002
